Checks will be made and if anything is sent which required import duties then it will be stopped
How do I know - well a parcel from the US is currently "held" by the Dutch postal service for me since early August and pending "processing". I had to fill in a 3 page document to explain it was a gift, and a month later still don't have a clue when I will receive it, or if I have to pay!
Within the EU though this should not be a problem as goods are alredy customs cleared (I used to work in Logistics for an International company importing goods and then trans-shipping within the EU)Answer 2
It won't go through customs no. You do not need to submit paperwork (commercial or proforma invoices) either.
The sorting hubs DO xray parcels though and will stop any prohibited items.
If you are enquiring because of duty and vat customs payments then the answer is "there won't be any!"Answer 3
Not generally, but they do random checks for unauthorized items, like tobacco products in excess quantities.